With a progress in electronic technology in recent years, a telephone, notebook type personal computer, audio/visual equipment or mobile terminal equipment is downsized; as a result, these devices have been rapidly widespread as a mobile electronic device. A fuel cell power source has been considered as a power source for a mobile electronic device. Since a fuel cell electrochemically and directly converts chemical energy possessed by a fuel into electric energy, it does not require a power section such as a generator using an internal combustion engine, which is an ordinary engine generator. Therefore, it has high practicability as a compact power-generating device. Further, the fuel cell continues a motive power generation so long as a fuel is replenished thereto; it is unnecessary to temporarily stop an operation of a device such as a load for charge, like the case where a normal secondary battery is used.
Widely known fuel cells are those wherein hydrogen generated by reforming city gas or the like is used as a fuel. An operation temperature of this type of fuel cells is not lower than 80° C. Fuel cells operating at a room temperature include the one wherein a liquid fuel is directly oxidized at a fuel electrode of the fuel cell; the typical one is a direct methanol fuel cell (DMFC) wherein methanol is directly oxidized.
A method for supplying a fuel to a fuel cell includes the one wherein a fuel for a power generation is sealed in a fuel cartridge and this fuel cartridge is mounted on the fuel cell, thereby supplying the fuel for a power generation to the fuel cell from the fuel cartridge via a fuel supply interface (e.g., see Patent Reference 1).
[Patent Reference 1]
Japanese Patent Laid-Open No. 2003-45468 (Summary)
A mixed solution of methanol and pure water has been studied as a fuel for a direct methanol fuel cell. An appropriate range is present in the methanol concentration in the mixed solution depending upon characteristics of a fuel cell. If a fuel having a concentration which is greatly outside the appropriate range is supplied to the fuel cell, the fuel cell does not exhibits a satisfactory output performance of the fuel cell, and further, adverse effects may possibly be given to components composing the fuel cell. Therefore, there arises a subject that it is necessary to detect whether a fuel contained in a fuel cartridge is appropriate for the fuel cell or not.